From: "Ard Biesheuvel" <ard.biesheuvel@arm.com>
To: Leif Lindholm <leif@nuviainc.com>, devel@edk2.groups.io
Cc: Michael D Kinney <michael.d.kinney@intel.com>,
Liming Gao <gaoliming@byosoft.com.cn>,
Zhiguang Liu <zhiguang.liu@intel.com>
Subject: Re: [PATCH 3/5] MdePkg/BaseLib: use normal register init in ARM SetJump implementations
Date: Tue, 13 Oct 2020 14:16:42 +0200 [thread overview]
Message-ID: <efab6bcf-bab6-c5da-ea63-c0d55beaea9b@arm.com> (raw)
In-Reply-To: <20201001183712.1738-4-leif@nuviainc.com>
On 10/1/20 8:37 PM, Leif Lindholm wrote:
> There may be architectures on which there are benefits to
> eor r0, r0(, r0)
> but ARM was never one of them. Change to more readable
> mov r0, #0
> instead.
>
> Signed-off-by: Leif Lindholm <leif@nuviainc.com>
> ---
> MdePkg/Library/BaseLib/Arm/SetJumpLongJump.S | 2 +-
> MdePkg/Library/BaseLib/Arm/SetJumpLongJump.asm | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/MdePkg/Library/BaseLib/Arm/SetJumpLongJump.S b/MdePkg/Library/BaseLib/Arm/SetJumpLongJump.S
> index 54b11ad2197c..407df5f41ac5 100644
> --- a/MdePkg/Library/BaseLib/Arm/SetJumpLongJump.S
> +++ b/MdePkg/Library/BaseLib/Arm/SetJumpLongJump.S
> @@ -36,7 +36,7 @@ ASM_PFX(SetJump):
> pop {r0, lr}
> mov r3, r13
> stmia r0, {r3-r12,r14}
> - eor r0, r0, r0
> + mov r0, #0
Actually, 'movs r0, #0' produces a smaller opcode here when building in
Thumb2 mode :-)
> bx lr
>
> #/**
> diff --git a/MdePkg/Library/BaseLib/Arm/SetJumpLongJump.asm b/MdePkg/Library/BaseLib/Arm/SetJumpLongJump.asm
> index 6d47033975f2..3a45f045460a 100644
> --- a/MdePkg/Library/BaseLib/Arm/SetJumpLongJump.asm
> +++ b/MdePkg/Library/BaseLib/Arm/SetJumpLongJump.asm
> @@ -36,7 +36,7 @@ SetJump
> POP {R0, LR}
> MOV R3, R13
> STM R0, {R3-R12,R14}
> - EOR R0, R0
> + MOV RO, #0
> BX LR
>
> ;/**
>
next prev parent reply other threads:[~2020-10-13 12:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-01 18:37 [PATCH 0/5] MdePkg: various fixes to ARM/AArch64 SetJump/LongJump Leif Lindholm
2020-10-01 18:37 ` [PATCH 1/5] MdePkg/BaseLib: fix comments in ARM* SetJump/LongJump implementations Leif Lindholm
2020-10-01 18:37 ` [PATCH 2/5] MdePkg/BaseLib: add ASSERT in ARM* SetJump implementations Leif Lindholm
2020-10-01 20:49 ` Ard Biesheuvel
2020-10-01 20:55 ` Leif Lindholm
2020-10-01 20:58 ` Ard Biesheuvel
2020-10-01 18:37 ` [PATCH 3/5] MdePkg/BaseLib: use normal register init in ARM " Leif Lindholm
2020-10-05 8:17 ` [edk2-devel] " Philippe Mathieu-Daudé
2020-10-13 12:16 ` Ard Biesheuvel [this message]
2020-10-01 18:37 ` [PATCH 4/5] MdePkg/BaseLib: correct register sizes in AArch64 SetJump/LongJump Leif Lindholm
2020-10-05 8:19 ` [edk2-devel] " Philippe Mathieu-Daudé
2020-10-01 18:37 ` [PATCH 5/5] MdePkg/BaseLib: ensure ARM LongJump never returns 0 Leif Lindholm
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